In view of decreasing world crude oil reserves and the discussion about the environmentally damaging consequences of the use of fossil and mineral fuels, there is increasing interest in alternative energy sources based on renewable raw materials. These include in particular natural oils and fats of vegetable or animal origin. These are generally triglycerides of fatty acids having from 10 to 24 carbon atoms and a calorific value comparable to conventional fuels, but are at the same time classified as biodegradable and environmentally compatible. In general, such oils contain glycerides from a series of acids whose number and type vary with the source of the oil, and they may additionally contain phosphoglycerides. Such oils can be obtained by processes known in the prior art.
US Patent Publication No. 2004/0010072 discloses the use of additives for improving the cold flow behavior of vegetable or animal fuel oils and to correspondingly additized fuel oils which contain fatty acid esters of monohydric alcohols which are derived, for example, from rapeseed oil, sunflower oil and/or soya oil and attain cold filter plugging point (CFPP) values of −20° C. and below which remain constant even when the oil is stored for a prolonged period in the region of its cloud point or below. The additive comprises ethylene copolymers, comb polymers and optionally polyalkyl (meth)acrylates and is a flow improver for such fatty acid esters.
Random copolymers made by ATRP have been used as pour point depressants (PPD) (U.S. Pat. No. 6,391,996), and viscosity index improvers for lubricating oil (US2002/0188081). The '996 patent mentions that the ATRP process could be used for blocky copolymers, but it fails to exemplify such a use, or disclose the benefits of using such block copolymers in bio-derived fuels.
The polymers disclosed in U.S. Pat. No. 6,391,996 are prepared via a controlled reaction described as using initiators having a transferable atomic group and a catalyst containing a transition metal (ATRP techniques). These types of polymerizations have several drawbacks including, but not limited to, slow polymerization kinetics, residual metallic byproducts, and limited polymer composition and molecular weight ranges. The residual metal catalysts can be detrimental for many applications as they influence the product properties and impact environmental compatibility.
These references do not disclose the use of a controlled architecture polymers having at least one pure acrylic block segment for use as a cold flow additives for bio-derived fuels.
U.S. Pat. No. 5,002,676 describes the preparation of block copolymers containing selectively hydrogenated conjugated dienes and t-butyl methacrylate. U.S. Pat. No. 6,350,723 teaches the synthesis of block copolymers through the living anionic polymerization of a conjugated diene and an alkyl methacylate monomer. These references exemplify the use of block copolymers containing conjugated dienes and hydrogenated dienes. These patents do not teach the significance of tailoring block composition or allow for the formation of gradient compositions. Furthermore, living anionic polymerization suffers from several drawbacks, such as, ineffectiveness at temperatures above −20° C., poor co-polymerization between polar and non-polar co-monomers, and the inability to use monomers that can be easily deprotanated. Therefore functional monomers cannot be incorporated, and the co-polymerization of monomer mixtures can be problematic and/or unusable. Furthermore this process can be expensive and difficult or impractical to carry out on an industrial scale as bulk or emulsion techniques cannot be used, extremely pure reagents are necessary (even trace amounts of protic material inhibits polymerization), and an inert atmosphere is requisite.
The use of acrylic block copolymers formed by a controlled-radical polymerization method to modifying the low temperature flow behavior in lubricating oils, including, but not limited to lowering the pour point is disclosed in US Patent Publication No. 2006/0185903.
A process for preparing copolymers in the presence of a stable free radical from the nitroxide family is described in U.S. Pat. No. 6,255,402. Nitroxide-mediated stable radicals have been used to produce controlled block copolymers, as described in U.S. Pat. No. 6,255,448, US 2002/0040117, and US Published Application No. 2005/0107577. These references, incorporated herein by reference, do not disclose the use of the copolymers in bio-derived fuels.